The present invention is directed to a conveyor belt scraper blade for use in a primary conveyor belt cleaner, and in particular to a scraper blade having a base member and a scraping member spaced apart from and connected to the base member by a resiliently flexible connector member and by a hinge member such that the scraping member is resiliently pivotal with respect to the base member.
Conveyor belts that carry highly abrasive bulk materials, such as iron-ore, wear faster at the center of the conveyor belt than at the edges of the conveyor belt. This differential in conveyor belt wear is due to a greater loading of the abrasive bulk material at the center of the belt than at the edges of the belt, such that the center of the belt carries a larger portion of the weight of the conveyed bulk material than do the edges of the belt. The scraper blades of a conveyor belt cleaner that are located at the center of the conveyor belt also wear faster than the scraper blades that are located at the edges of the conveyor belt. Fine carry back material often remains adhered to the conveyor belt after the conveyed material has been discharged from the belt. The fine carry back material is more heavily concentrated at the center of the belt than at the edges of the belt. This causes a differential in wear between scraper blades of a conveyor belt cleaner that are located at the center of the belt and scraper blades that are located at the edges of the conveyor belt. The combination of these two conditions, increased loading and a greater amount of carry back material at the center of the belt, causes accelerated wear to the center of the conveyor belt and to the scraper blades of a conventional conveyor belt cleaner that are located at the center of the belt. The differential in the wear of the conveyor belt and in the wear of the scraper blades of a conveyor belt cleaner results in a generally elongate elliptical-shaped cavity being formed between the conveyor belt and the scraper blades at the center of the belt that quickly grows in size and that allows unacceptable quantities of carry back material to pass beyond the conveyor belt cleaner.
Conventional primary conveyor belt cleaner scraper blades are mounted on a cross shaft that is rotated about the longitudinal axis of the shaft to tension the scraper blades against the belt. Any compensation for differential wear rates between the center of the belt and the edges of the belt is provided for by the elasticity of the material from which the scraper blades are formed. Typically, conventional scraper blades can only bend or flex a few degrees to accommodate differential wear in the conveyor belt or unevenness in the surface of the pulley about which the conveyor belt rotates. For belts carrying normally abrasive bulk materials, such as coal, this few degrees of compensation for differential wear is adequate. However, when highly abrasive materials, such as iron-ore, are conveyed this limited amount of compensation is inadequate.
Elastomeric materials all take some compression set so that when an elastomeric scraper blade is flexed or deflected under load, over time it does not fully rebound or return to its original position. In addition, the elastomeric materials that are best suited for wear resistance tend not to be the elastomeric materials that have optimum compression set properties. This results in unacceptable design trade-offs. Materials with optimum properties for maintaining a constant amount of resilient rebound after deflection include engineering materials such as spring steel and composite materials. These materials can function as springs when deformed within their elastic limits. However, such materials are not suitable materials from which to make primary scraper blades due to the high cost of the material and the possibility of the material causing damage to the conveyor belt. The scraper blade of the present invention makes use of the desirable properties of elastomers and of engineering materials such as spring steel to overcome the above problems.
The scraper blade of the present invention can easily accommodate up to fifteen degrees of rotation or pivotal movement of the scraping member of the scraper blade with respect to the base member of the scraper blade, without creating an excessive cleaning pressure between the scraper blade and the conveyor belt, which would otherwise result by pivoting the scraping tip of a conventional elastomeric scraper blade the same fifteen degrees, or even just ten degrees, with respect to its base member. A fifteen degree compensation for differential wear of the conveyor belt and of the scraper blades on a conveyor belt cleaner is sufficient to efficiently clean a conveyor belt carrying highly abrasive materials.
A scraper blade adapted to be mounted on a cross shaft of a conveyor belt cleaner wherein the cross shaft is selectively movable, either by rotation about a rotational axis or by linear movement. The scraper blade includes a scraping member having a lower foot portion and a tip having a scraping edge. The foot and the tip are formed from an elastomeric material. The scraper blade also includes a base member formed from an elastomeric material that is adapted to be attached to the cross shaft of the conveyor belt cleaner. The base member is spaced apart from, but is located in relatively close proximity to, the foot of the scraping member. One or more resiliently flexible connector members, such as metal springs, extend between the base member and the foot of the scraping member. Each connector member has a first end attached to and embedded within the foot of the scraping member and a second end attached to and embedded within the base member. A hinge member extends between a top surface of the base member and a bottom surface of the foot of the scraping member and embeds the portions of the connector members that are located between the base member and the scraping member. The hinge member may be formed from an elastomeric material that is substantially softer than the elastomeric material that forms the scraping member and the base member or from the same elastomeric material that forms the scraping member. The hinge member includes a generally concave front surface and a generally concave rear surface that form a hinge plane. The resiliently flexible connector members and the hinge member enable the scraping member to resiliently pivot with respect to the base member about a pivot axis that is located between the base member and the scraping member without any movement of the base member.